mpi-mul.c
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/* mpi-mul.c - MPI functions
* Copyright (C) 1994, 1996, 1998, 2001, 2002,
* 2003 Free Software Foundation, Inc.
*
* This file is part of Libgcrypt.
*
* Note: This code is heavily based on the GNU MP Library.
* Actually it's the same code with only minor changes in the
* way the data is stored; this is to support the abstraction
* of an optional secure memory allocation which may be used
* to avoid revealing of sensitive data due to paging etc.
*/
#include "mpi-internal.h"
void mpi_mul(MPI w, MPI u, MPI v)
{
mpi_size_t usize, vsize, wsize;
mpi_ptr_t up, vp, wp;
mpi_limb_t cy;
int usign, vsign, sign_product;
int assign_wp = 0;
mpi_ptr_t tmp_limb = NULL;
if (u->nlimbs < v->nlimbs) {
/* Swap U and V. */
usize = v->nlimbs;
usign = v->sign;
up = v->d;
vsize = u->nlimbs;
vsign = u->sign;
vp = u->d;
} else {
usize = u->nlimbs;
usign = u->sign;
up = u->d;
vsize = v->nlimbs;
vsign = v->sign;
vp = v->d;
}
sign_product = usign ^ vsign;
wp = w->d;
/* Ensure W has space enough to store the result. */
wsize = usize + vsize;
if (w->alloced < wsize) {
if (wp == up || wp == vp) {
wp = mpi_alloc_limb_space(wsize);
assign_wp = 1;
} else {
mpi_resize(w, wsize);
wp = w->d;
}
} else { /* Make U and V not overlap with W. */
if (wp == up) {
/* W and U are identical. Allocate temporary space for U. */
up = tmp_limb = mpi_alloc_limb_space(usize);
/* Is V identical too? Keep it identical with U. */
if (wp == vp)
vp = up;
/* Copy to the temporary space. */
MPN_COPY(up, wp, usize);
} else if (wp == vp) {
/* W and V are identical. Allocate temporary space for V. */
vp = tmp_limb = mpi_alloc_limb_space(vsize);
/* Copy to the temporary space. */
MPN_COPY(vp, wp, vsize);
}
}
if (!vsize)
wsize = 0;
else {
mpihelp_mul(wp, up, usize, vp, vsize, &cy);
wsize -= cy ? 0:1;
}
if (assign_wp)
mpi_assign_limb_space(w, wp, wsize);
w->nlimbs = wsize;
w->sign = sign_product;
if (tmp_limb)
mpi_free_limb_space(tmp_limb);
}
void mpi_mulm(MPI w, MPI u, MPI v, MPI m)
{
mpi_mul(w, u, v);
mpi_tdiv_r(w, w, m);
}
EXPORT_SYMBOL_GPL(mpi_mulm);